Semi-automatic dilution pipette



May 18, 1965 s. T. NERENBERG SEMI-AUTOMATIC DILU'IION PIPETTE 2Sheets-Sheet 2 Filed Aug. 2'7, 1962 Fig.4.

mvzm'oa Samuel T. Nerenberg BY United States Patent 3,184,122ElrH-AUTQMATE DILUTIQN PEPETTE Samuel T. Nerenberg, (Ihiidrens Hospital,Maple and Qaliiornia Sta, San Francisco 18, Calif. Filed Aug. 27, 1962,Ser. No. 219,62? 4 Claims. (Cl. 222-255) This invention relates todilution devices. More particularly it relates to dilution pipettes ofthe type capable of discharging a constant volume of sample and avariable known volume of diluent therefor.

Briefiy, in the preferred embodiment the present device includes apipette calibrated for holding and discharging a known volume of samplesolution. A predetermined volume of diluent is supplied from a diluentmetering chamber of adjustable volume to said pipette for discharge inconjunction with the sample solution and dilution thereof to acalculable concentration.

The diluent is supplied to the diluent metering chamber from a diluentstorage chamber. The diluent storage chamber is linked by means of aconduit to a vacuum chamber so that the vacuum chamber and diluentstorage chamber are in air communication only with each other. Thevacuum chamber is linked for fluid communication with the pipette by aconduit. When diluent is removed from the storage chamber for supplyingthe metering chamber, a partial vacuum or negative pressure is createdin the storage chamber. The partial vacuum is in turn created in thevacuum chamber. This vacuum may be used for drawing sample solution intothe pipette since the pipette is linked thereto. Suitable valves areprovided between the various members so that air and liquid may be urgedinto and from the various chambers in proper sequence. Pumping means isprovided for moving the fluids to their appropriate locations.

In the accompanying drawings there is shown in:

FIG. 1 a side view partially in section of part of the device of thepresent invention including a pair of pipettes, cylinders and plungersand associated valves.

FIG. 2 shows in end elevation the means for selecting and limiting theextent of withdrawal of the plunger from the cylinder so that the volumeof the cylinder may be adjusted and is taken along the line 2-2 of FIG.1.

FIG. 3 shows in side elevation with portions broken away a secondposition of the 2-way valve shown on the right hand side of PEG. 1.

FIG. 4 shows schematically the device of the present invention.

The primary object of the present invention is to provide a dilutionpipette capable of rapid repetitive use that is of sutlicient mechanicalsimplicity so that it may be constructed at a relatively low cost whileremaining substantially free from stoppages.

A more specific object is to provide a dilution pipette wherein thepipette is filled with sample solution to be diluted by means ofnegative pressure and the negative pressure is provided internally andautomatically by operation of the device itself.

A further object is to provide a dilution device wherein the volume ofdiluent supplied per volume of sample solution is adjustable so that theconcentration of diluted sample solution may be selected as desired.

A further object is to provide a dilution device wherein the volume ofdiluent to be supplied may be adjustably fixed for rapid and rigidoperation Without the necessity of adjusting the dilution volume foreach volume of sample solution to be diluted.

Further objects, features, and advantages of the present invention willbecome apparent upon reading the following detailed specification whenread in conjunction with the accompanying drawings.

Patented hlay id, 1955 With respect to the schematic diagram shown inFIG. 4 the general mode of operation of the present device will beillustrated first. Diluent is stored in diluent storage chamber A. Aportion of the diluent is drawn into diluent metering chamber B bywithdrawal therefrom of pumping means or plunger C. The volume ofdiluent drawn into diluent metering chamber B will be determined by theextent of Withdrawal of plunger C.

When a portion of the diluent is removed from diluent storage chamber A,a partial vacuum is created in diluent storage chamber A above the levelof the liquid diluent therein. This partial vacuum is in turn impartedto vacuum chamber D through conduit E.

A 2-way valve F is provided for alternately linking calibrated pipette Gwith diluent metering chamber B and vacuum chamber D. When 2-way valve Flinks pipette G with vacuum chamber D and pipette G is immersed in asource of sample solution, the sample solution will be drawn so as tofill pipette G and into conduit H which links pipette G with chamber D.Positioning of 2-Way valve P so that diluent metering chamber B is thenplaced in communication with pipette G permits the discharge of samplesolution in pipette G with the diluent in diluent metering chamber B byactuation or downward movement of plunger C. Suitable valves arepositioned in conduits I and l as will be explained hereinafter so thatliquids are movable only in the aforementioned paths and are notpermitted to b forced into the wrong conduits.

Vacuum chamber D serves as a sample liquid trap so that the diluent isnot contaminated in diluent storage chamber A. Any suitable device whichserves to trap excess sample fluid from pipette G but allows negativepressure from storage chamber A to reach valve F may be used.

Also illustrated in E56. 4 at th left hand side is another cooperatingset of a pipette G, valve F, cylinder B, plunger C, storage chamber A,and corresponding linking conduits. This corresponding unit is linked tothe aforesaid described unit in common with vacuum chamber D. By havingsuch a plurality of units it is possible to provide different diluentsin readiness for diluting the same or difierent sample solutions.

More specifically with respect. to FIGS. 1-3, the present preferredembodiment includes pipette G of known volume in fluid communicationwith 2-way valve F. When valve F is in its second position with valveplug lil vertically aligned as shown in FIG. 1, pipette G is placed influid communication with vacuum chamber D (as in FIG. 4) through conduitH. When 2-way valve F is placed in its first position by rotationthereof so that valve plug it) is horizontal as illustrated in FIG. 3,pipette G is placed in fluid communication with conduit 3.

Conduit J includes a tubular body 12 fitted on projection 13 of 2-wayvalve F. Int'eriorly of tubular body 12, a check valve la is urgedagainst valve seat 15 by spring to. Flow of fluid toward pipette G movesvalve 14 against spring 16 to open the valve and permit fluid to fiowthrough tubular body 12 to pipette G when 2-way valve F is in its firstposition. For reasons that will become clear hereinafter, when negativepressures are developed on the side of valve 14 away from pipette G,valve 14 is drawn against valve seat 15 preventing fluid flow throughtubular body 12.

Conduit I links tubular body 12 with diluent storage chamber A, A valvehousing 17 links conduit I with tubular body 12. A check valve 13similar to valve 14- permits flow from conduit 1 into tubular body 12while prohibiting fluid from flowing in the opposite direct-ion.

A cylinder 1? is threada'bly engaged at neck 2d of tubular body 12. Aplunger 21 is mounted for reciprocal 9 movement within cylinder 19, Whenplunger 21 is drawn upwardly, negative pressure is created in. meteringchamber 22 defined by cylinder 19. The negative pressure causes valve 14to seat itself in valve seat 15 while causing valve 18 to open and fluidto be drawn through conduit I from storage chamber A into meteringchamber 22 until the space vacated in chamber 22 by plunger 21 is filledwith fluid from storage chamber A.

When plunger 21 is thereafter moved downwardly through metering chamber22 of cylinder 19, the diluent fluid previously drawn therein during theupward withdrawal stroke of plunger 21 will be forced outwardly fromchamber 22 through tubular body 12 and into pipette G when plug of 2-wayvalve F is positioned horizontally as in FIG. 3, This action causes bothdischarge of sample solution which may be in pipette G and discharge ofdiluent through pipette G for mixture with the sample solution. Sincethe volume of pipette G is known, if the volume of metering chamber 22is also known for each position or extent of upward withdrawal ofplunger 21, the concentration of the sample of fluid when mixed withdiluent may be readily calculated as 'wiil be obvious to those skilledin the art.

When the diluent in chamber 22 is being forced through pipette G duringthe downward stroke of plunger 21, the pressure created by the diluentforces valve 13 to close against valve seat 23 to prevent return ofdiluent to storage chamber A At the same time the downward pressure ofthe diluent forces valve 14 away from valve seat so that the diluent canpass into pipette G through 'valve F.

It should be noted that the entire volume of metering chamber 22 doesnot pass into pipette G since a portion thereof will remain in tubularbody 12.. However, since the amount of fluid remaining in tubular body112 is con stant, it will not interfere with the calibration of the volume of metering chamber '22 for the various positions of withdrawal ofplunger 21 therefrom.

Cylinder l9 and plunger 21 may be conveniently mounted in verticalposition on a bracket 24 supported by arms 25 and 26 which are in turnadjustably supported by screws 45, 46 on a stand, a segment of theupright portion of which is shown at 27 in FIG, 2. The top of plunger 21is fixed to head 28 by coupling 29. Coupling 29 has an opening at 3%through which the top of plunger 21 is inserted and flanged over at 31so that plunger 21 cannot be pulled downwardly out of coupling 29. A setscrew 32 holds head 28 interiorly in fixed relative relation to coupling29.

Cylinder 19 is supported on bottom leg 33 of bracket 24 by means ofthreadedly engaged members 34, 35. Member 34- is frictionally engagedwith the upper end of cylinder 1% and member 35 is joined with the lowersurface or leg 33.

By forcing head 28 downwardly, plunger 21 is simultaneouslyfo-rceddownwardly through hole 47 (defined in leg 33) into cylinder 21.A spring 36 inserted between lip 48 on coupling 29 and the top of member35 appearing in hole 47 of leg 33 is compressed during this downwardmotion. When head 28 is released and no longer urged downwardly, spring36 returns plunger 21 and head 28 to its upward position and therebycauses the withdrawal of plunger 21 from cylinder 19.

The extent of withdrawal of plunger 21 may be adjustably selected bymeans of collar 37 and set screw 38. By tightening set screw 38 andfastening collar 37 on head 28 at any particular position along thelongitudinal axis of head 23, the position of maximum withdrawal ofplunger 21 from cylinder 19 is determined. This is due to upper leg 39on bracket 24. When head 28 is urged upwardly by spring 36, collar 37engages leg 39 and further upward movement of head 28 is prevented, Byfixing collar'37 on head 28 with set screw 38, plunger 21 may beoperated repeatedly by urging downwardly on end 28 and the volumeprovided in metering chamber 22 3 will remain constant until collar 37is moved to another position.

The volume of metering chamber 22 is suitably calibrated :for thevarious positions of collar 37 on head 28 with respect to thelongitudinal axis thereof. Suitable graduations may be placed on head 28for indication of the volume of diluent which will be drawn intometering chamber 22 for discharge therefrom through pipette G.

Head 28 may suitably be urged downwardly by means of lever 49 and wheel41, Lever 46 is pivotally mounted on supporting upright 42 which is inturn supported by bracket 24 and leg 39 thereof.

The various components on the left hand side of the device asillustrated in FIG, 1 are in all ways similar to the device on the righthand side as described above. Both sides of the device may be suitablyoperated by lever 40 by first pivoting lever 4d about supporting upright42 so that wheel 41 contacts and is in position for depressing head 23as shown in FIG. 1. After depressing head 23, lever td may be pivoted tothe right hand side so that wheel d1 engages head 28 for the downwardstroke.

Although the foregoing invention has been described in some detail byWay of illustration and example for purposes of clarity ofunderstanding, it is understood that certain changes and modificationsmay be practiced within the spirit of the invention as limited only bythe scope of the appended claims.

What is claimed is:

l. A dilution pipette capable of repeatedly dispensing a constant volumeof sample solution and a preselected volume of diluent thereforcomprising a calibrated sample solution chamber having a port foringress of sample solution and for subsequent discharge of the chambervolume of sample solution and a preselected volume of diluent, a diluentmetering chamber of adjustable volume for holding diluent, conduit meansestablishing fluid communication between said diluent metering chamberand said sample solution chamber, a 2-way valve having first and secondpositions between said sample solution chamber and said diluent meteringchamber permitting fluid communication therebetween when in said firstposition, valve means between said 2-way valve and said diluent meteringchamber for pemitting fluid movement between said 2-way valve and saiddiluent metering chamber only towards said 2-way valve, a diluentstorage chamber, a conduit establishing fluid communication between saiddiluent storage chamber and said diluent metering chamber, valve meansbetween said storage chamber and metering chamber permitting fluid flowtherebetween only toward said metering chamber, a vacuum chamber, aconduit for establishing air communication only between said storagechamber and said vacuum chamber, a conduit establishing fluidcommunication between said vacuum chamber and said sample solutionchamber through said 2-way valve when the 2-way valve is in its secondposition, and pumping means operable to urge diluent from said storagechamber to fill said metering chamber to a preselected volume bycreating negative pressure in said metering chamber which therebycreates a partial vacuum in said storage chamber and in turn in saidvacuum chamber, said partial vacuum serving to draw sample solution intosaid sample solution chamber when said 2-way valve is in its secondposition, said pumping means then being operable to discharge apredetermined volume of the diluent urged into the diluent meteringchamber through the sample solution chamber and its port along with thesample solution in the sample chamber when said 2-way valve is in itsfirst position.

2. A dilution pipette in accordance with claim 1 wherein said diluentmetering chamber comprises a cylinder and said pumping means comprises aplunger inserted for reciprocal movement Within said cylinder.

3. A dilution pipette in accordance with claim 2 wherein the volume ofsaid diluent metering chamber is adjusted "by selecting the extent ofwithdrawal of said plunger from said cylinder and including means forpreselectively limiting the extent of Withdrawal of said plunger fromthe cylinder for repeated filling and discharge of a constant volumefrom said diluent metering chamber to said sample solution chamber.

4. A dilution pipette in accordance with claim 1 and including aplurality of sets of sample chambers, diluent References (Iited by theExaminer UNITED STATES PATENTS 2,089,796 8/37 Hopf et al. 23-259 X2,798,647 7/57 Broadwin 2223O9 3,012,863 12/61 Fe-ichtmeir 23259 X3,033,656 5/62 Saifer et al 23-253 X LOUIS J, DEMBO, Primary Examiner.

ROBERT EVANS, Examiner.

1. A DILUTION PIPETTE CAPABLE OF REPEATEDLY DISPENSING A CONSTANT VOLUMEOF SAMPLE SOLUTION AND A PRESELECTED VOLUME OF DILUENT THEREFORCOMPRISING A CALIBRATED SAMPLE SOLUTION CHAMBER HAVING A PORT FORINGRESS OF SAMPLE SOLUTION AND FOR SUBSEQUENT DISCHARGE OF THE CHAMBERVOLUME OF SAMPLE SOLUTION AND A PRESELECTED VOLUME OF DILUENT, A DILUENTMETERING CHAMBER OF ADJUSTABLE VOLUME FOR HOLDING DILUENT, CONDUIT MEANSESTABLISHING FLUID COMMUNICATING BETWEEN SAID DILUENT METERING CHAMBERAND SAID SAMPLE SOLUTION CHAMBER, A 2-WAY VALVE HAVING FIRST AND SECONDPOSITIONS BETWEEN SAID SAMPLE SOLUTION CHAMBER AND SAID DILUENT METERINGCHAMBER PERMITTING FLUID COMMUNICATION THEREBETWEEN WHEN IN SAID FIRSTPOSITION, VALVE MEANS BETWEEN SAID 2-WAY VALVE AND SAID DILUENT METERINGCHAMBER FOR PERMITTING FLUID MOVEMENT BETWEEN SAID 2-WAY VALVE AND SAIDDILUENT METERING CHAMBER ONLY TOWARDS SAID 2-WAY VALVE, A DILUENTSTORAGE CHAMBER, A CONDUIT ESTABLISHING FLUID COMMUNICATION BETWEEN SAIDDILUENT STORAGE CHAMBER AND SAID DILUENT METERING CHAMBER, VALVE MEANSBETWEEN SAID STORAGE CHAMBER AND METERING CHAMBER PERMITTING FLUID FLOWTHEREBETWEEN ONLY TOWARD